hg grep: handle re.compile errors & update tests/test-grep

mercurial/commands.py

@@ -1092,7 +1092,11 b' def grep(ui, repo, pattern, *pats, **opt'
     reflags = 0
     if opts['ignore_case']:
         reflags |= re.I
-    regexp = re.compile(pattern, reflags)
+    try:
+        regexp = re.compile(pattern, reflags)
+    except Exception, inst:
+        ui.warn(_("grep: invalid match pattern: %s!\n") % inst)
+        return None
     sep, eol = ':', '\n'
     if opts['print0']:
         sep = eol = '\0'

tests/test-grep

@@ -17,6 +17,8 b" hg commit -m 3 -u eggs -d '3 0'"
 head -n 3 port > port1
 mv port1 port
 hg commit -m 4 -u spam -d '4 0'
+echo % pattern error
+hg grep '**test**'
 echo % simple
 hg grep port port
 echo % all

tests/test-grep.out

@@ -1,3 +1,5 b''
+% pattern error
+grep: invalid match pattern: nothing to repeat!
 % simple
 port:4:export
 port:4:vaportight